Electromagnetic transducer heads



Aug. 23, 1966 F. J. LOHAN 3,268,878

ELECTROMAGNETIC TRANSDUCER HEADS Filed 0013. 10, 1962 INVENTOR. flQA/VK Jim/AN BY 4 T TOE'NE Y5 3,268,873 1C6 Patented Aug 1966 3,268,878 ELECTRUMAGNETIC TRANSDUCER HEADS Frank J. Lohan, Detroit, Mich, assignor to Ex-Celi-O Corporation, Detroit, Mich.

Fiied Get. 10, 1962, Ser. No. 229,687 25 Claims. (Cl. 340-174.1)

This invention relates to electromagnetic transducers in general, and in particular to improvements in the construction of electromagnetic transducers of the type used for imparting intelligence upon and reading intelligence from a magnetizable surface as are commonly found in intelligence recording and reproducing devices.

One object of this invention is to provide an electromagnetic transducer which is simple in construction and can be manufactured and assembled with relative ease utilizing a minimum number of parts including a commercially available component and other elements which may be easily standardized, inherently resulting in a small, light package of inexpensive construction, and in a greatly reduced parts inventory.

Another object of this invention is to provide an electromagnetic transducer which can be aflixed to a variety of holding devices (head mounts) which are used to maintain the position of the transducer relative to the recording surface.

A further object of this invention is to provide an electromagnetic transducer in whose structure magnetic shielding is realized by virtue of construction.

Still another object of this invention is to provide an electromagnetic transducer so designed as to permit the sub-assembly of the critical pol-e pieces and gap spacer to be effected in a precision manner and the remainder of the assembly to be effected in a non-precision manner yet realizing high performance.

A further object of this invention is to provide a transducer head assembly having a substantially large surface area in the plane of the flux deflecting gap, thus providing a transducer head capable of being supported by the laminar film of fluid set in motion by the moving recording medium, thereby eliminating the requirement of mounting the transducer head in a bearing pad or shoe in applications where it is desired to obtain a non-contact fluid borne transducer head.

Further objects and advantages of the invention will be more readily appreciated by reference to the following description taken in connection with the accompanying drawings, in which like numerals refer to like elements, and wherein:

FIGURE 1 is an exploded perspective view of an embodiment of an electromagnetic transducer according to the principle of the invention;

FIGURE 2 is a perspective end view of the electro magnetic transducer of FIGURE 1 showing more particularly the structural arrangement of the pole pieces;

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 2;

FIGURE 4 is an exploded perspective view of an alternate embodiment of an electromagnetic transducer according to the invention;

FIGURE 5 is a perspective end view of the electromagnetic transducer of FIGURE 4 showing more particularly the structural arrangement of the pole pieces;

FIGURE 6 is a sectional view taken along line 6-6 of FIGURE 5;

FIGURE 7 is an exploded perspective view of another alternate embodiment of an electromagnetic transducer according to the invention;

FIGURE 8 is a sectional view taken along the axis of symmetry of the embodiment shown in FIGURE 7; and

FIGURE 9 is a sectional view taken along line 9-9 of FIGURE 8.

Referring now to the drawings, and more particularly to FIGURES 1-3, a cup core 10, which is preferably a commercially available standard part made of a magnetic material such as ferrite or the like, constitutes a first magnetic core section of the electromagnetic transducer of the invention.

The cup core 10 is provided with an annular flange portion 12 extending outwardly from a cup base 14. The cup core 10 is also provided with a cylindrical post portion 16 disposed within the annular flange portion 12 substantially coaxially thereto and which is appreciably shorter than the height of the annular flange portion 12. An aperture is provided in the cup core 10, affording a passage for the lead-in wires of a magnetizing coil 2.0; such an aperture is advantageously a slot 18 in the annular flange portion 12, as shown in the drawings, or it may alternately be a hole (not shown) in the cup base 14.

The magnetizing or transducer coil 20 is disposed around the post portion 16 for inducing a variable magnetic flux through the flux loop during recording operation, or for transducing a variable magnetic flux into a variable electrical signal during reading or playback operation, as is well-known to those versed in the art.

The coil 20 is made of wound electric wire having for example two terminal wires 22-72 and a center tap wire 24, which pass through the apertl' re or slot 18 previously mentioned. The selection of the :oil 21) depends primarily on the magnetic characteristit s desired for each spe cific application of the electromagnetic transducer.

A second magnetic core sectior. or bar 26, substantially parallelepipedonic in shape, is d sposed with its longitudinal axis extending radially with one side surface proximate one end thereof in intimae contact with end face 28 of the post portion 16 ant". with the other end 29 forming a first pole piece.

A third magnetic core section 30 is placed in intimate Contact with end face 32 of the annular flange portion 12 of the cup core 10. The core section 30 is substantially shaped as a cylindrical segment of the same radius as and concentric to the annular flange portion 12 of the cup core 11). The core section 30 is disposed in such a manner as to present a rectangular face 42 normal to the longitudinal axis of the second magnetic core section 26 thus forming a second pole piece.

A thin sliver of flux-deflecting non-magnetic material, or gap spacer 44, is disposed between and in intimate contact with the pole piece faces 29 and 42, thus forcing the magnetic flux loop to close through the magnetizable recording surface (not shown).

The constitutive elements of the electromagnetic transducer are assembled in the manner hitherto illustrated and described, and bound firmly together by a process of impregnation with a suitable bonding or potting material 46, which is subsequently cured for a determined period.

The active end face of the transducer assembly is then ground and lapped providing a surface which is substantially flush with the core sections 26 and 30, and that surface may be coated, if so desired, with polytetrafluoroethylene or a similar material to provide a smooth and unctuous surface with a low coefficient of friction which will prevent damage to either the recording surface or to the core sections 2630 if the transducer is placed in contact with the record surface.

It will be obvious to anyone skilled in the art that the electromagnetic transducer of the invention is capable of being mounted in many different manners relatively to a record medium. For example, the transducer may be mounted in a fixed mount establishing a predetermined air gap between the pole pieces and the surface of the record medium. It may also be mounted on a resilient mounting means enabling the transducer to be supported by the film of laminar fluid set in motion by the moving record medium as a result of the substantially large surface area of the transducer end face surrounding the pole pieces.

It can also be seen that the coil 20 is almost entirely surrounded by the magnetic material of the cup core 10, thus providing a coil substantially shielded against stray magnetic interferences without the added requirement of disposing the transducer within a shielding enclosure.

FIGURES 4-6 represent an alternate embodiment in which the cup core 10, the transducer coil 20, the parallelepipedonic core section 26, and the gap spacer 44 are similar in construction, composition, and function as shown and described in relation to the previous embodiment. The sole difference is in the third magnetic core section 48 which is in the form of an annulus. A flat surface 50, on the inner cylindrical surface 52 of the core section 48 defines a pole piece separated by gap spacer 44 from the pole piece 29 defined by the end face of second magnetic core section or bar 26.

The modification of FIGURES 7-9 comprises the same constitutive elements as are present in the precedently described embodiments of the invention, eliminating however the third magnetic core section and imposing directly on the inner surface 54 of the annular flange portion 12 a flat surface 56 defining one of the pole pieces of the transducer, the other pole piece being defined, as hereinbefore explained, by the end face 29 of the magnetic core section or bar 26.

The specific embodiments described in the above specification and illustrated in the accompanying drawings are merely illustrative of several forms, which the invention may take in practice and it will be understood by those skilled in the art that various changes in details may be made therein without departing from the spirit and scope of the invention.

What is claimed as new is:

1. An electromagnetic transducer comprising: a first magnetic cup-shaped core section provided with an integral annular flange portion disposed substantially coaxially around an integral post portion; a magnetizing coil disposed around said post portion in the space between said post portion and said annular flange portion; a second magnetic core section extending radially from said post portion, a side surface proximate one end of said second magnetic core section being in intimate contact with the end face of said post portion and another end of said second magnetic core section forming a first pole piece; a third core section in intimate contact with the face of the annular flange portion of said first magnetic core section, said third core section presenting a face forming a second pole piece opposite said first pole piece; a sliver of flux deflecting material disposed between said first and second pole pieces; and a potting and bonding material maintaining said core sections and coil together and filling all the voids and cavities therebetween, said pole pieces being substantially flush with the surface of said plotting and bonding material.

2. The electromagnetic transducer of claim 1 wherein the annular flange portion of said first magnetic core section is provided with an aperture affording a passage for lead-in wires connected to the magnetizing coil.

3. The electromagnetic transducer of claim 1 wherein said third magnetic core section is a segment-shaped block of magnetic material.

4. The electromagnetic transducer of claim 1 wherein said third magnetic core section is an annular member of magnetic material.

5. The electromagnetic transducer of claim 1 wherein the surface of the potting and bonding material is ground and lapped even with the outer surface of the pole pieces.

6. The electromagnetic transducer of claim 5 wherein the ground and lapped surface is coated with an unctuous material.

7. An electromagnetic transducer comprising: a first magnetic cup-shaped core section provided with an integral annular flange portion disposed substantially coaxially around an integral post portion; a magnetizing coil disposed around said post portion in the space between said post portion and said annular flange portion; a second magnetic core section extending radially from said post portion and having one end in intimate contact with said post portion and another end forming a first pole piece; a third core section in intimate contact with the annular flange portion of said first magnetic core section, said third core section presenting a face forming a second pole piece opposite said first pole piece; a sliver of flux deflecting material disposed between said first and second pole pieces; and a potting and bonding material maintaining said core sections and coil together and filling all the voids and cavities therebetween, said pole pieces being substantially flush with the surface of said potting and bonding material.

8. The electromagnetic transducer of claim 7 wherein the annular flange portion of said first magnetic core section is provided with an aperture affording a passage for the lead-in wires connected to the magnetizing coil.

9. The electromagnetic transducer of claim 7 wherein said third magnetic core section is a segment-shaped block of magnetic material.

10. The electromagnetic transducer of claim 7 wherein said third magnetic core section is an annular member of magnetic material.

11. The electromagnetic transducer of claim 7 wherein the surface of the potting and bonding material is ground and lapped even with the outer surface of the pole pieces.

12. The electromagnetic transducer of claim 11 wherein the ground and lapped surface is coated with an unctuous material.

13. An electromagnetic transducer comprising: a first magnetic cup-shaped core section provided with an integral annular flange portion disposed substantially coaxially around an integral post portion; a magnetizing coil disposed around said post portion in the space between said post portion and said annular flange portion; a second magnetic core section extending radially from said post portion, a side surface proximate one end of said second magnetic core section being in intimate contact with the end face of said post portion and another end of said magnetic core section forming a first pole piece; a flat surface disposed on the inner surface of the annular flange portion forming a second pole piece; a sliver of flux deflecting material disposed between said first and second pole pieces; and a potting and bonding material maintaining said core sections and coil together and filling all the void and cavities therebetween, said pole pieces being substantially flush with the surface of said potting material.

14-. The electromagnetic transducer of claim 13 wherein the annular flange portion of said first magnetic core section is provided with an aperture affording a passage for lead-in wires connected to the magnetizing coil.

15. An electromagnetic transducer comprising: a first magnetic cup-shaped core section provided with an integral annular flange portion disposed substantially coaxially around an integral post portion; a magnetizing coil disposed around said post portion in the space between said post portion and said annular flange portion; a second magnetic core section extending radially from said post portion and having one end in intimate contact with said post portion and another end forming a first pole piece; a flat surface disposed on the inner surface of the annular flange portion forming a second pole piece; a sliver of flux deflecting material disposed between said first and second pole pieces; and a potting and bonding material maintaining said core sections and coil together and filling all the void and cavities therebetween, said pole pieces being substantially flush with the surface of said potting material.

16. A method of manufacturing an electromagnetic transducer utilizing in such manufacture a commercially available magnetic material cup core comprising a central post and an annular flange coaxial therewith, said method comprising: machining a substantially small flat face on the inner surface of said annular flange of said cup core; said flat face being parallel to the axis of said cup core and defining a pole piece therein; disposing a flux inducing electric coil around said central post; placing a magnetic material bridge member radially to said cup core with a side surface of one end of said bridge member in intimate contact with said post and the other end of said bridge member disposed parallely said flat face and defining another pole piece; inserting a sliver of flux deflecting material between said pole pieces; impregnating with a bonding and potting material to a level substantially flush with the outer surface of said pole pieces; and curing and hardening said bonding and potting material.

17. A method of manufacturing an electromagnetic transducer utilizing in such manufacture a commercially available magnetic material cup core comprising a central post and an annular flange coaxial therewith, said method comprising: disposing a flux inducing electric coil around said central post; placing a magnetic material bridge member radially to said cup core with a side surface of one end of said bridge member in intimate contact with the terminal end face of said post and the other end of said bridge member having a flat surface defining a first pole piece; disposing a member of magnetic material in intimate contact with the annular flange of said cup core, said member presenting a flat surface substantially parallel the flat surface on the end of said bridge member and defining a second pole piece; inserting a sliver of flux deflecting material between said first and second pole pieces; impregnating with a bonding and potting material to a level substantially flush with the outer surface of said pole pieces; and curing and hardening said bonding and potting material.

18. The method defined in claim 17 with the added step of grind-ing and lapping the surface of the hardened bonding and potting material even with the pole pieces outer face.

19. The method defined in claim 18 with the added step of coating the ground and lapped surface with an unctuous material.

20. A method of manufacturing an electromagnetic transducer utilizing in such manufacture a commercially available magnetic material cup core comprising a central post and an annular flange coaxial therewith, said method comprising: disposing a flux inducing electric coil around said central post; placing a magnetic material bridge member radially to said cup core with one end of said bridge member in intimate contact with said post and the other end of said bridge member having a flat surface defining a first pole piece; disposing a member of magnetic material in intimate contact with the annular flange of said cup core, said member presenting a flat surface substantially parallel the flat surface on the end of said bridge member and defining a second pole piece; inserting a sliver of flux detecting material between said first and second pole pieces; impregnating with a bonding: and potting material to a level substantially flush with the outer surface of said pole pieces; and curing and hardening said bonding and potting material.

21. The method defined in claim 20 with the added step of grinding and lapping the surface of the hardened bonding and potting material even with the pole pieces outer face.

22. The method defined in claim 21 with the added step of coating the ground lapped surface with an unctuous material.

23. A method of manufacturing an electromagnetic transducer utilizing in such manufacture a commercially available magnetic material cup core comprising a central post and an annular flange coaxial therewith, said method comprising: disposing a flux inducing electric coil around said central post; placing a magnetic material bridge member radially to said cup core with a side surface of one end of said bridge member in intimate contact with the terminal end face of said post and the other end of said bridge member having a flat surface defining a first pole piece; disposing a member of magnetic material in intimate contact with the end face of the annular flange of said cup core, said member presenting a flat surface substantially parallel the flat surface on the end of said bridge member and defining a second pole piece; inserting a sliver of flux detecting material between said. first and second pole pieces; impregnating with a bonding and potting material to a level substantially flush with the outer surf-ace of said pole pieces; and curing and hardening said bonding and potting material.

24. The method defined in claim 23 with the added step of grinding and lapping the surface of the hardened bonding and potting material even with the pole pieces outer face.

25. The method defined in claim 24 with the added step of coating the ground and lapped surface with an unctuous material.

No references cited.

BERNARD KONICK, Primary Examiner.

A. I. NEUSTADT, Assistant Examiner. 

1. AN ELECTROMAGNETIC TRANSDUCER COMPRISING: A FIRST MAGNETIC CUP-SHAPED CORE SECTION PROVIDED WITH AN INTEGRAL ANNULAR FLANGE PORTION DISPOSED SUBSTANTIALLY COAXIALLY AROUND AN INTEGRAL POST PORTION; MAGNETIZING COIL DISPOSED AROUND SAID POST PORTION IN THE SPACE BETWEEN SAID POST PORTION AND SAID ANNULAR FLANGE PORTION; A SECOND MAGNETIC CORE SECTION EXTENDING RADIALLY FROM SAID POST PORITON, A SIDE SURFACE PROXIMATE ONE END OF SAID SECOND MAGNETIC CORE SECTION BEING IN INTIMATE CONTACT WITH THE END FACE OF SAID POST PORTION AND ANOTHER END OF SAID SECOND MAGNETIC CORE SECTION FORMING A FIRST POLE PIECE; A THIRD CORE SECTION IN INTIMATE CONTACT WITH THE FACE OF THE ANNULAR FLANGE PORTION OF SAID FIRST MAGNETIC CORE SECTION, SAID THIRD CORE SECTION PRESENTING A FACE FORMING A SECOND POLE PIECE OPPOSITE SAID FIRST POLE PIECE; A SLIVER OF FLUX DEFLECTING MATERIAL DISPOSED BETWEEN SAID FIRST AND SECOND POLE PIECES; AND A POTTING AND BONDING MATERIAL MAINTAINING SAID CORE SECTIONS AND COIL TOGETHER AND FILLING ALL THE VOIDS AND CAVITIES THEREBETWEEN, SAID POLE PIECES BEING SUBSTANTIALLY FLUSH WITH THE SURFACE OF SAID PLOTTING AND BONDING MATERIAL. 